Plastic lenses are lightweight, highly tough and easy to be dyed. Properties particularly required for plastic lenses are: low specific gravity; high transparency; low yellowness; high refractive index and high Abbe number as optical properties; high heat resistance; high strength; and the like. A high refractive index allows a lens to be thinner, and a high Abbe number reduces the chromatic aberration of a lens.
Recently, many optical materials using an organic compound having a sulfur atom for providing a high refractive index and a high Abbe number have been reported.
Among such optical materials, polyepisulfide compounds having a sulfur atom are known to provide a good balance between the refractive index and the Abbe number (Patent Document 1). High refractive indexes of 1.7 or higher were achieved by optical materials obtained from these polyepisulfide compounds. However, it has been desired to provide a material having a higher refractive index, and an optical material obtained by using a composition for optical materials containing an organic compound having a cyclic skeleton containing a sulfur, selenium or tellurium atom was proposed. Such ring compounds have a refractive index of 1.73 or higher (Patent Document 2).
However, in the case of such optical materials obtained by using a composition for optical materials having a high refractive index, heat resistance may be insufficient, mold release characteristics may be insufficient, and lenses may be easily broken at the time of demolding, and these are the problems.